The present invention relates generally to the data processing field, and more particularly, relates to a storage area network (SAN) fibre channel arbitrated loop (FCAL) multi-system, multi-resource storage enclosure, and a method for performing small computer system interface (SCSI) enclosure services (SES) node maintenance concurrent with device operations.
It is common in the computer industry to have a storage area network (SAN) that uses fibre channel arbitrated loop (FCAL) technology to connect multiple systems to multiple FCAL storage resources such as, for example, disk, tape, optical devices. Storage enclosures including multiple FCAL storage resources typically are used as part of the SANs. A small computer system interface (SCSI) enclosure services (SES) node is required to control resources such as power, LEDs, port bypass circuits (PBCs) and to collect status or general information such as device present, power good, vital product data (VPD) and the like.
As used in the following description and claims, it should be understood that the term SCSI in SCSI enclosure services (SES) node is a general term applicable to more than just physical SCSI components.
A conventional storage enclosure or storage box used as part of SANs presents a maintenance problem. Typical storage enclosures provide concurrent maintenance capability for devices, power supplies, and sometimes for adapters. However, failures of other active components, such as FCAL port bypass circuits (PBCs) typically located on the backplane of the storage enclosure, require the storage enclosure to be taken offline for service and repair. In a highly reliable, available system, outages to perform maintenance are very undesirable because of the loss of access to the data.
It is desirable to provide an improved storage area network (SAN) fibre channel arbitrated loop (FCAL) multi-system, multi-resource, storage enclosure. A need exists for such storage enclosure that provides improved reliability. It is desirable to provide such storage enclosure that enables maintenance to all active components while allowing the storage enclosure to remain online.
Principal objects of the present invention are to provide a storage area network (SAN) fibre channel arbitrated loop (FCAL) multi-system, multi-resource, storage enclosure and a method for performing enclosure maintenance concurrent with device operations. Other important objects of the present invention are to provide such storage enclosure and method substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, a storage area network (SAN) fibre channel arbitrated loop (FCAL) multiple system, multiple resource, storage enclosure and a method are provided for performing enclosure maintenance concurrent with device operations. The storage enclosure includes a plurality of storage resources or storage devices, a plurality of IO adapters (IOAs) coupled to the storage area network and a pair of enclosure services node cards. Each enclosure services node card includes loop connections for the plurality of storage resources. Each enclosure services node card includes a respective global bus connection and a loop connection to each of the plurality of IOAs. Each enclosure services node card is used concurrently by the multiple systems to manage the plurality of storage resources. In the method for performing enclosure maintenance concurrent with device operations, identical maintenance procedures are implemented for the enclosure services node cards and the storage devices.
In accordance with features of the invention, the enclosure services node cards are removable cards and contain active components including port bypass circuits (PBCs). Fibre channel (FC) connections for the plurality of storage resources provide redundant paths to each storage resource and allows access to data on the storage resources to continue when one of the pair of enclosure services node cards fails or is being maintained. Out of band communications to the enclosure services node cards are provided with the global buses, such as I2C buses, rather than FC loop. Multiple IOAs can concurrently use the same enclosure services node card without contention or collision.